Bacterial infections caused by gram-positive bacteria such as Streptococcus, Staphylococcus, Enterococcus, Bacillus, Corynebacterium, Listeria, Erysipelothrix, and Clostridium and by gram-negative bacteria such as Haemophilus, Shigella, Vibrio cholerae, Neisseria and certain types of Escherichia coli cause serious morbidity throughout the world. This, coupled with the emerging resistance shown by bacteria to antibiotics, indicates the need for the development of bacterial vaccines. For example, streptococci are a large and varied genus of gram-positive bacteria which have been ordered into several groups based on the antigenicity and structure of their cell wall polysaccharide (26, 27). Two of these groups have been associated with serious human infections. The group A streptococci cause a variety of infectious disorders including "strep throat", rheumatic fever, streptococcal impetigo, and sepsis.
Group B streptococci were not known as human pathogens in standard medical textbooks until the early 1970's. Since that time, studies have shown that group B streptococci are important perinatal pathogens in the United States as well as developing countries (37). Systemic group B streptococcal infections during the first two months of life affect approximately three out of every 1000 births (12), resulting in 11,000 cases annually in the United States. These infections cause symptoms of congenital pneumonia, sepsis, and meningitis. A substantial number of these infants die or have permanent neurological sequelae. Furthermore, group B streptococcal infections may be implicated in the high pregnancy-related morbidity which occurs in nearly 50,000 women annually. Others at risk from group B streptococcal infections are those who have an altered immune response, either congenitally, chemotherapeutically, or by other means.
Group B streptococci can be further classified into several different types based on the bacteria's capsular polysaccharide. Types Ia, lb, II, III, IV, V, VI, VII, and VIII account for most of the pathogenicity due to group B infection, with group B streptococci types Ia, Ib, II, III, and V representing over 90% of all reported cases. The structure of each of these various type polysaccharides has been characterized (19-22, 44). Similar to findings with many other human bacterial pathogens, capsular polysaccharides of group B streptococci, when used in vaccines, may provide effective protection against infections with these bacteria. See 4, 6, 24, 29, 30, 42, 43, 45.
Gram-negative bacteria are also a significant cause of disease. Until the recent development and use of polysaccharide-proteinvaccines directed against Haemophilus influenzae type b bacteria (Hib), Hib bacterial infections were responsible for many cases of mental retardation in infants. N. menigitidis and E. coli K1 infections are responsible for neonatal meningitis. Strains of gram-negative bacteria, E. coli, have been linked to serious illness including death from eating meat tainted with E. coli strains.
Large-scale production of capsular polysaccharide vaccines, and capsular polysaccharide conjugate vaccines, requires adequate supplies of purified capsular polysaccharides. Prior art methods (40, 42) for isolating capsular polysaccharides from bacterial cells rely on treatment of cells with the enzyme mutanolysin. Mutanolysin cleaves the bacterial cell wall which frees the cellular components. This procedure involves treating cell lysates with additional enzymes to remove proteins and nucleic acids and purification by differential precipitation and chromatography. More efficient, higher yielding and simpler means of obtaining purified capsular polysaccharides are desirable.